Gregory et al. Journal of Cardiovascular Magnetic
Resonance 2014, 16(Suppl 1):P148
http://www.jcmr-online.com/content/16/S1/P148
POSTER PRESENTATION
Open Access
Comparing 3DQRS and VCG approaches for ECG
QRS detection within 1.5T, 3T and 7T MRI
Thomas S Gregory1*, Ehud J Schmidt2, Shelley H Zhang2, Zion T Tse1
From 17th Annual SCMR Scientific Sessions
New Orleans, LA, USA. 16-19 January 2014
Background
Electrocardiograms (ECGs) obtained within High-field
MRIs are distorted due to the Magneto-hydrodynamic
(MHD) effect. Blood plasma electrolytes ejected into the
aorta during early systole interact with the strong magnetic field of the MR scanner to produce a MHD-induced
voltage (VMHD) [1]. The VMHD overlay on ECG traces
can result in intermittent QRS detection. Vectorcardiogram (VCG) based gating approaches have been conventionally adapted in most MRI scanners [2], but may fail at
high field strengths [3]. Recently, a multiple ECG channel
cross-correlation based algorithm, 3DQRS, has been developed to provide increased sensitivity levels in these environments [4]. The 3DQRS approach constructs a 3-D ECG
representation, where the third dimension, in addition to
voltage and time, is deemed a channels axis, formed from
concurrent viewing of the precordial leads V1-V6.
This study quantitatively compares 3DQRS and VCG
approaches at a variety of MRI field strengths to assess the
robustness of these methods.
Methods
12-lead ECG data was recorded using a prototype MRIconditional 12-lead ECG recorder [5] from 2 Premature
Ventricular Contraction (PVC) patients, 2 Atrial Fibrillation (AF) patients, and a healthy exercising athlete at 1.5T
and 3T [4]. A Halter recorder was used in 2 healthy volunteers at 7T [6] (Figure 1a-f). QRS detection was performed
using a VCG-based approach (V1-V6, I, II) [2] and 3DQRS
(V1-V6) using standard 12-lead ECG chest positioning [4].
Assessments of 3DQRS robustness relative to variations in
field strength and cross-correlation kernel temporal length
were performed (Figure 1g-h). False Positive (FP) and False
Negative (FN) counts were recorded (total of 1,262 beats)
in order to assess the sensitivity for QRS detection for each
method at 1.5T, 3T, and 7T.
Results
Table 1 shows the gating results for 3DQRS and VCG
at 1.5T, 3T, and 7T in various subjects. 3DQRS subjectaveraged accuracy levels in QRS detection (False
Negative), relative to VCG, were: 1.5T (100% vs. 96.6%),
3T (98.1% vs. 87%), 7T (96% vs. 71.2%). In PVC patients
at 1.5T, 3DQRS separated between the SR and PVC beats
with 100% accuracy, whereas VCG falsely detected PVC
beats, which were of similar length and magnitude to the
sinus rhythm beats, with only 37.3% accuracy (Table 1).
Conclusions
The 3DQRS method represented a higher sensitivity in
QRS detection than the VCG based approach, which
resulted in decreased error levels in high field MRI.
Funding
NIH U41-RR019703, NIH R03 EB013873-01A1, SBIR-1
R43 HL110427-01.
1
College of Engineering, University of Georgia, Athens, Georgia, USA
Full list of author information is available at the end of the article
© 2014 Gregory et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative
Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and
reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver
(http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
Gregory et al. Journal of Cardiovascular Magnetic
Resonance 2014, 16(Suppl 1):P148
http://www.jcmr-online.com/content/16/S1/P148
Page 2 of 3
Figure 1 (a-f) Representative 2 cardiac cycles of the precordial leads V1-V6 for patients and volunteers at various field strengths
("Rpeak” denotes the R-wave peak positions). (g-h) 3DQRS performance evaluation, showing its performance at various field strengths.
Table 1 Results of 3DQRS and VCG Efficacy Tests at 1.5T, 3T, and 7T
–
1.5T
3T
7T
3DQRS
VCG-based
Marked
False Negative
False Positive
False Negative
False Positive
PVC at 1.5T
0
0
2
Total Beats
37
Percent of Total
0.0%
0.0%
3.4%
62.7%
–
–
–
–
–
–
–
AF-Diagnosed #1 at 3T
3
1
3
6
45
AF-Diagnosed #2 at 3T
1
1
34
18
169
Exercising Athlete at 3T
2
2
41
46
316
316
59
Total Count
6
4
41
46
Percent of Total
1.9%
1.3%
13.0%
14.6%
–
–
–
–
–
–
–
Healthy Subject #1 at 7T
6
6
175
156
382
Healthy Subject #2 at 7T
29
30
80
56
505
Total Count
35
36
255
212
887
Percent of Total
4.0%
4.1%
28.8%
23.9%
–
Gregory et al. Journal of Cardiovascular Magnetic
Resonance 2014, 16(Suppl 1):P148
http://www.jcmr-online.com/content/16/S1/P148
Page 3 of 3
Authors’ details
1
College of Engineering, University of Georgia, Athens, Georgia, USA.
2
Brigham and Women’s Hospital, Boston, Massachusetts, USA.
Published: 16 January 2014
References
1. Gupta: IEEE Trans Bio Med Eng 2008.
2. Fischer: MRM 1999.
3. Krug: JCMR 2013.
4. Tse: JCMR 2013.
5. Tse: MRM 2013.
6. Krug: CompInCardiol 2012.
doi:10.1186/1532-429X-16-S1-P148
Cite this article as: Gregory et al.: Comparing 3DQRS and VCG
approaches for ECG QRS detection within 1.5T, 3T and 7T MRI. Journal
of Cardiovascular Magnetic Resonance 2014 16(Suppl 1):P148.
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